145 
A PrystograrpHic Survey or tHe Terre Haute ArEa— 
Report oF PROGRESS. 
By CHARLES R. DRYER, 
The physiographic survey of the Terre Haute area reported last year 
has been continued during the past season and extended across the Wabash 
valley to the top of the east bluffs. <A strip six miles wide, north and south, 
has been completed, and we have been brought face to face with the prob- 
lem of the sand and gravel terrace, three miles and more in width, 50 feet 
above the river and more than 100 feet deep, which extends along the east 
side of the valley a distance of 30 niles. Within the area surveyed its 
generally level surface is traversed by several irregular north-south 
ridges, which rise to a nearly uniform height of 510 feet A. T. These are 
interpreted as being bars laid down by a loaded and probably braided 
stream. In some places these bars are capped by subsequent eolian de- 
posits. The materials of the terrace are everywhere fairly well assorted 
and stratified, with frequent cross bedding, where the strata dip down 
stream and suggest local delta formation. The strata in vertical section 
often display a great variety and testify to frequent local changes in the 
velocity of the depositing stream. Boulders up to two or three feet in 
diameter are common and are attributed to the melting of floating ice. 
The terrace heads 12 miles north of Terre Haute in Parke Co., where 
the Shelbyville moraine of the Wisconsin ice sheet crossed the Wabash 
valley. At this point the problem is complicated by the extension of the 
terrace up the valley of Raccoon creek to the northeast where it is more 
than a mile wide. The final solution requires the extension of the survey 
to the Shelbyville moraine and up the Raccoon valley to a distance not yet 
determined. This work has been begun, but is not yet completed. So far 
as studied, the terrace appears to be an outwash plain, or valley train, 
laid Gown by a constantly overloaded stream, or streams, which issued 
from the margin of the Wisconsin ice sheet. Whether this is the true in- 
terpretation, whether the train originally occupied the whole width of the 
valley, and, if so, what were the agencies and conditions of its removal from 
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